Histopathology of cerebral toxoplasmosis in human immunodeficiency virus infection: a comparison between patients with early-onset and late-onset acquired immunodeficiency syndrome.

We reviewed the histological features of untreated toxoplasmosis in 18 cases with the acquired immunodeficiency syndrome (AIDS), eight of which were surgical biopsies and 10 of which were autopsy specimens. The results were compared according to the clinical status of the patient at the time the diagnosis of toxoplasmosis was made (early-onset v late-onset AIDS) and according to the source of the specimen (surgical biopsy specimen v autopsy specimen). Cerebral toxoplasmosis was the AIDS-defining illness in half of the cases (six surgical biopsy specimens and three autopsy specimens). Inflammation in these cases was moderate in 44% and severe in 56%. Fibrous capsules were found in five cases. Lymphocytes and plasma cells were more prominent than neutrophils. Cerebral toxoplasmosis developed in or was part of the terminal AIDS illness in the remaining nine cases (two surgical biopsy specimens and seven autopsy specimens). In this group inflammation was sparse in 44%, moderate in 55%, and severe in only 11%. Fibrous capsules were usually absent and neutrophils were the predominant cell type. Comparisons between surgical biopsy specimens and autopsy specimens showed moderate to severe inflammation and frequent fibrous encapsulation in all of the former specimens but only in those autopsy specimens in which toxoplasmosis was the initial manifestation of AIDS. Thus, this study demonstrates varied neuropathological patterns of untreated cerebral toxoplasmosis in patients with AIDS and correlates the inflammatory response in the brain with the clinical stage of the patient's human immunodeficiency syndrome (HIV) infection. Inflammation and fibrous encapsulation were common only in patients with early-onset AIDS in whom cerebral toxoplasmosis was the first manifestation of the illness. This study highlights important differences between the histology of this infection at surgical biopsy and at autopsy, and stresses the need to consider toxoplasma as a potential cause of encapsulated brain abscesses.